The following invention relates generally to oil well shock absorbers for the sucker rod which pumps oil when reciprocated axially.
The following represents an improvement over my earlier U.S. Pat. No. 3,021,794 entitled "Oil Well Pumping Rod Shock Absorber". In the operation of an oil well pump, the fluid stands somewhere in the pumping valve or cylinder causing the associated well rod to slap in its associated shroud or tubing which results in wearing down of the tubing walls ultimately causing openings to occur. The slap of the rods also result in unnecessary wear with the result that the well is in need of repair relatively prematurely, and it becomes necessary to replace both the worn rods and the tubing. As is common in wells, a section of casing is disposed within the ground and provided with a plurality of perforations at a lowermost portion thereof which encourages the liquid to be pumped to seep therewithin. Annularly disposed within the casing is a further perforated pipe placed below a section of pipe defined as a working barrel and axially aligned therewith. The working barrel extends primarily into a casing section which is nonforaminous and the working barrel includes a means for attachment to the perforated pipe. Slidably disposed therewithin a working valve allows vertical reciprocal motion of a valve rod to pump the oil up within the "working barrel". Thus, a stand valve which discourages fluid migration in one direction and the working valve operate in concert to cause unidirectional fluid flow up within the working barrel, the working valve attached to the surface by means of a valve rod and ultimately the oil well sucker rod shock absorber according to the instant invention. Disposed imediately above the sucker rod shock absorber a sucker rod is attached so that the oil well sucker rod shock absorber comes into play when the working valve and its associated valve rod bottom out, a phenomena know as "pounding the level".
The following patents reflect the state of the art of which applicant is aware insofar as these citations appear germane to the process at hand.
U.S. Pat. No. 2,087,590, Brazell PA1 U.S. Pat. No. 2,834,294, Schoen.
Brazell teaches the use of a known prior art device suitably formed and adapted to remove sand from a well proximate to where the pump is located. To this end, a pump is lowered into a well until it is obvious that the pump has landed on the bottom, and a plunger associated therewith will move downwardly to the lower end of the pump when the tension on a cable associated therewith is released. Fluid beneath the plunger passes upwardly through mandrel, past the valve and out the opening. Once the upward pull of the cable is effected, the plunger will move upwardly and a load of sand will be drawn from the reservoir into the barrel. As the plunger is elevated, spring will yield and be placed under a certain amount of compression thus acting as a shock absorber to the extent of relieving the sudden tension on a cable when the plunger has reached the limit of upward movement. At that point the spring will expand to its former position. Thus, the spring associated therewith merely serves to assure that the plunger will return to an original position and its inherent spring qualities serve to damp the momentum associated with extreme cable motion.
Similarly, the patent to Schoen relates generally to a shifter device reciprocating with a connecting rod and hence with the sucker pump. An overtravel spring cage and its associated spring provide overtravel compensation for the shifter device as shown in FIG. 2. Clearly, the structure associated therewith is prone to "a fluid block" due in part to the incompressibility of the associated fluid, and its likelihood of seepage into the overtravel area, providing a hydraulic ram effect, contrary to its intended purpose.
By way of contrast therefore, the instant invention contemplates a shock absorber unit designed to be positioned on the lower end of a well rod whereby the operation of the well rod is smooth and easy and wherein slap and wear resulting therefrom is reduced to a minimum. To this end, the oil well sucker rod shock absorber according to the instant application is serially connected to a lower portion of a sucker rod disposed first in a working barrel which is annularly inserted within an oil well casing. Thereafter, a lower portion of the sucker rod shock absorber is attached to a valve rod adapted to axially reciprocate in response to sucker rod vertical translation. The valve rod is ultimately connected to a working valve and a stand valve adapted to encourage the unidirectional flow of oil or other liquids within the working barrel.